include-sql is a macro for using SQL in Rust.

include-sql was inspired by Yesql. It allows the programmer to write SQL queries in SQL, keep them separate from the Rust code, and easily embed them into Rust programs via the proc-macro that this library provides.

All by itself include-sql actually does very little - it reads and parses SQL file and transforms it into a call to the impl_sql macro. It is expected that impl_sql is provided either by the project that uses include-sql or by an external library. For example, there are several include-sql companion crates, like include-postgres-sql and include-sqlite-sql, that implement impl_sql. They can simply be used directly if their approaches to embedding SQL are deemed appropriate and convenient. Alternatively, they can be used as a starting point when implementing your own impl_sql.

Example

As include-sql is not intended to be used directly, to illustrate the workflow we'll use include-sqlite-sql.

Add include-sqlite-sql as a dependency:

toml [dependencies] include-sqlite-sql = "0.1"

Write your SQL and save it in a file. For example, let's say the following is saved as library.sql in the project's src folder:

```sql -- name: getloanedbooks? -- Returns the list of books loaned to a patron -- # Parameters -- param: userid: &str - user ID SELECT booktitle FROM library WHERE loanedto = :userid ORDER BY 1;

-- name: loanbooks! -- Updates the book records to reflect loan to a patron -- # Parameters -- param: userid: &str - user ID -- param: bookids: u32 - book IDs UPDATE library SET loanedto = :userid , loanedon = currenttimestamp WHERE bookid IN (:book_ids); ```

And then use it in Rust as:

```rust , ignore use includesqlitesql::{includesql, implsql}; use rusqlite::{Result, Connection};

include_sql!("src/library.sql");

fn main() -> Result<()> { let args : Vec = std::env::args().collect(); let dbpath = &args[1]; let user_id = &args[2];

let db = Connection::open(dbpath)?;

db.get_loaned_books(user_id, |row| {
    let book_title : &str = row.get_ref("book_title")?.as_str()?;
    println!("{}", book_title);
    Ok(())
})?;

Ok(())

} ```

Note that the path to the SQL file must be specified relative to the project root, i.e. relative to CARGO_MANIFEST_DIR, even if you keep your SQL file alongside rust module that includes it. Because include-sql targets stable Rust this requirement will persist until SourceFile stabilizes.

Under the Hood

After parsing and validating the content of the SQL file include-sql generates the following call:

rust , ignore impl_sql!{ LibrarySql = { ? get_loaned_books (:user_id (&str)) " Returns the list of books loaned to a patron\n # Parameters\n * `user_id` - user ID" $ "SELECT book_title\n FROM library\n WHERE loaned_to = " :user_id "\n ORDER BY 1" }, { ! loan_books (:user_id (&str) #book_ids (u32)) " Updates the book records to reflect loan to a patron\n # Parameters\n * `user_id` - user ID\n * `book_ids` - book IDs" $ "UPDATE library\n SET loaned_to = " :user_id "\n, loaned_on = current_timestamp\n WHERE book_id IN (" #book_ids ")" } }

Which include_sqlite_sql::impl_sql transforms into the following implementation:

``rust , ignore trait LibrarySql { /// Returns the list of books loaned to a patron /// # Parameters /// *userid` - user ID fn getloanedbooks(&self, userid: &str, rowcallback: F) -> rusqlite::Result<()> where F: Fn(&rusqlite::Row<'>) -> rusqlite::Result<()>;

/// Updates the book records to reflect loan to a patron
/// # Parameters
/// * `user_id` - user ID
/// * `book_ids` - book IDs
fn loan_books(&self, user_id: &str, book_ids: &[u32]) -> rusqlite::Result<usize>;

} ```

And, of course, it also implements the trait:

rust , ignore impl LibrarySql for rusqlite::Connection { /// ... }

Documentation

The included documentation describes the supported SQL file format and provides instructions on writing your own impl_sql macro.